Systems and Methods for Regenerating A Spent Catalyst

ABSTRACT

Systems and methods for regenerating a spent catalyst are provided. The method can include mixing a spent catalyst with a carrier fluid to provide a mixture. The spent catalyst can include carbon deposited on at least a portion thereof. The carrier fluid can include an oxygen containing gas. The mixture can be introduced to or above an upper surface of a dense phase catalyst zone disposed within a regenerator. A gas can be introduced to a lower zone of the dense phase catalyst zone. At least a portion of the carbon deposited on the catalyst can be combusted to provide a flue gas, heat, and a regenerated catalyst.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to systems and methods for processing hydrocarbons. More particularly, embodiments of the present invention relate to systems and methods for regenerating spent catalyst.

2. Description of the Related Art

Fluid catalytic crackers (“FCC”) are a mainstay in the conversion of raw hydrocarbons into one or more products. An FCC consists of few components: one or more riser reactors, one or more disengagers, and one or more regenerators. A hydrocarbon feed and one or more catalysts are introduced to the riser reactor which is maintained at an elevated temperature and/or pressure. The cracking of the hydrocarbons within the riser reactor produces one or more cracked hydrocarbons and small quantities carbonaceous coke which is deposited on the surface of the catalyst. The coke includes mostly carbon, but also contains hydrogen, sulfur, nitrogen, and trace amounts of other elements. These coke deposits reduce the catalyst activity after passage through the riser reactor. The cracked hydrocarbons and the coked catalyst or (“spent catalyst”) exit the riser reactor and are introduced to one or more disengagers where the spent catalyst is separated from the cracked hydrocarbons. The cracked hydrocarbons are removed from the FCC for further processing and/or treatment. The spent catalyst is introduced to one or more regenerators where the coke is combusted, oxidized, and/or converted to one or more waste gases.

The combustion process removes coke from the surface of the catalyst, regenerating the catalyst, and permitting its recycle back to the riser reactor. However, the combustion process generates undesirable byproducts, such as nitrogen oxides (“NOx”), which must be removed or at least partially reduced to meet environmental regulations.

There is a need, therefore, for improved systems and methods for regenerating catalyst while producing less undesirable byproducts.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the recited features of the present invention can be understood in detail, a more particular description of the invention may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 depicts a partial cross-sectional view of an illustrative catalyst regeneration system having a spent catalyst distributor disposed above a dense phase catalyst bed, according to one or more embodiments described.

FIG. 2 depicts a partial cross-sectional view of an illustrative catalyst regeneration system having a spent catalyst distributor and fluid introduction nozzles disposed above a dense phase catalyst bed, according to one or more embodiments described.

FIG. 3 depicts a partial cross-sectional view of the illustrative catalyst regeneration system depicted in FIG. 1, further including an illustrative variable oxygen content carrier fluid generation system, according to one or more embodiments described.

FIG. 4 depicts a partial cross-sectional view of an illustrative catalyst regeneration system having a spent catalyst introduction line in fluid communication with a dense phase catalyst bed and one or more fluid introduction nozzles disposed above the dense phase catalyst bed, according to one or more embodiments described.

FIG. 5 depicts a partial cross-sectional top view of an illustrative catalyst regenerator, according to one or more embodiments described.

FIG. 6 depicts an illustrative fluid catalytic cracking system according to one or more embodiments described.

DETAILED DESCRIPTION

A detailed description will now be provided. Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims. Each of the inventions will now be described in greater detail below, including specific embodiments, versions and examples, but the inventions are not limited to these embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the inventions, when the information in this patent is combined with publicly available information and technology.

Systems and methods for regenerating a spent catalyst are provided. The method can include mixing a spent catalyst with a carrier fluid to provide a mixture. The spent catalyst can include carbon deposited on at least a portion thereof. The carrier fluid can include an oxygen containing gas. The mixture can be introduced to or above an upper surface of a dense phase catalyst zone disposed within a regenerator. A gas can be introduced to a lower zone of the dense phase catalyst zone. At least a portion of the carbon deposited on the catalyst can be combusted to provide a flue gas, heat, and a regenerated catalyst.

FIG. 1 depicts a partial cross-sectional view of an illustrative catalyst regeneration system 100 having a spent catalyst distributor 150 disposed above a dense phase catalyst bed 145, according to one or more embodiments. The catalyst regeneration system 100 can include one or more regenerators 140. The regenerator 140 can include the dense phase catalyst zone 145, a dilute phase catalyst zone 155, one or more distributors 150, one or more fluid introduction nozzles (two are shown 160), and one or more cyclones (two are shown 165).

The dense phase catalyst zone 145 can be disposed toward a first end 141 of the regenerator 140 and the dilute phase catalyst zone 155 can be disposed toward a second end 142 of the regenerator 140. The dilute phase catalyst zone 155 can have a spent catalyst and/or regenerated catalyst concentration ranging from a low of about 0 kg/m³, about 50 kg/m³, or about 100 kg/m³ to a high of about 140 kg/m³, about 160 kg/m³, about 175 kg/m³, or more. The dense phase catalyst zone 145 can have a spent catalyst and/or regenerated catalyst concentration ranging from a low of about 240 kg/m³, about 320 kg/m³, about 375 kg/m³ to a high of about 420 kg/m³, about 475 kg/m³, about 525 kg/m³, or more.

The dense phase catalyst zone 145 can be referred to as having a first or “lower” zone 146, a second or “middle” zone 147, and a third or “upper” zone 148. The regenerator 140, as shown in FIG. 1 and discussed and described herein, is with reference to a vertical, cylindrical, regenerator 140 with the dense phase catalyst zone 145 disposed below the dilute phase catalyst zone 155 and an L/D ratio of greater than 1, however, any orientation or configuration can be used.

The first zone 146 can include the lower portion or region of the dense phase catalyst zone 145. The third zone 148 can include the upper portion or region of the dense phase catalyst zone 145. The third zone 148 can also be referred to as a “transitional zone” that can span a region intermediate the dense phase catalyst zone 145 and the dilute phase catalyst zone 155. The transitional zone 148 can have a fluid bed density intermediate the density of the lower density dilute phase catalyst zone 155 and the higher density first and second catalyst zones 146, 147, respectively. The second zone 147 can include the middle portion or region disposed between the first zone 146 and the third zone 148.

In one or more embodiments, the one or more distributors 150 can be disposed within the transitional zone 148 between the surface 149 of the dense phase catalyst zone 145 and the second end 142 of the regenerator 140. The distributor 150 can include one or more ports or nozzles 152 to provide fluid communication from line 135, through the distributor 150 and to the regenerator 140. In at least one specific embodiment, the distributor 150 or at least the nozzles 152 can be disposed within the dense phase catalyst bed 145. For example, the distributor 150 or at least the nozzles 152 can be disposed within the third zone 148 of the dense phase catalyst zone 145. In another example, the distributor 150 or at least the nozzles 152 can be disposed within the second or middle zone 147.

In one or more embodiments, the fluid introduction nozzles 160 can be disposed within the dense phase catalyst zone 145 toward the first end 141 of the regenerator 140. For example, the fluid introduction nozzles 160 can be disposed within the first zone 146 of the dense phase catalyst zone 145.

A carrier fluid via line 130 and spent catalyst via line 131 can be introduced to line 135 to provide a mixture of spent catalyst and carrier fluid. The spent catalyst can include carbon or coke at least partially disposed thereon and/or therein. The mixture of spent catalyst and carrier fluid via line 135 can be introduced to the distributor 150, which can introduce the mixture to the regenerator 140 via the one or more exit ports or nozzles 152. In one or more embodiments, the distributor 150 can distribute the mixture about the surface 149 of the dense phase catalyst zone 145. In one or more embodiments, the distributor 150 can distribute the mixture above the surface 149 of the dense phase catalyst zone 145. For example, the mixture can be introduced to the dilute phase catalyst zone 155. In one or more embodiments, the distributor 150 can distribute the mixture beneath the surface 149 of the dense phase catalyst zone 145 and within the third zone 148 of the dense phase catalyst zone 145. In one or more embodiments, the distributor 150 can distribute a portion of the mixture above the surface 149 and a portion below the surface 149 of the dense phase catalyst zone 145. In one or more embodiments, the distributor 150 can distribute the mixture to the second or middle zone 147, the third or upper zone 148, the dilute phase catalyst zone 155, or any combination thereof.

The carrier fluid via line 130 can be or include any suitable fluid. Illustrative carrier fluids can include, but are not limited to, air, oxygen-lean gas, oxygen-rich gas, ozone, steam, carbon monoxide (“CO”), carbon dioxide (“CO₂”), combustion or exhaust gas, or any combination thereof. As used herein, the term “oxygen-lean” refers to a gas containing less oxygen than air. As used herein, the term “oxygen-rich” refers to a gas containing more oxygen than air.

A fluid or gas via line 119 can be introduced to the fluid introduction nozzles 160. The fluid can provide sufficient velocity or motive force within the dense phase catalyst zone 145 to provide a fluidized catalyst zone. In other words, the dense phase catalyst zone 145 can be a fluidized catalyst zone. The fluid introduced via nozzles 160 can flow through the dense phase catalyst zone 145 toward the second end 142 of the regenerator 140.

The fluid introduced via nozzles 160 can be any suitable fluid or mixture of fluids. For example, the fluid introduced via line 119 to the regenerator 140 can include, but is not limited to, air, oxygen-rich gas, oxygen-lean gas, ozone, CO, CO₂, nitrogen, steam, combustion or exhaust gas, or any combination thereof.

When the fluid introduced via nozzles 160 includes an oxidant, the fluid can flow through the dense phase zone 145 and the oxidant present can combust or otherwise burn at least a portion of the carbon or coke deposited on the spent catalyst and/or coke dust to provide a regenerated catalyst via line 177 and a combustion gas or flue gas via line 170. The regeneration, i.e. combustion of the coke deposited on and/or within the catalyst can re-expose the reactive surfaces of the catalyst, thereby regenerating the catalyst and permitting reuse. The flue gas can contain oxygen, CO, CO₂, NOx, and/or sulfur oxides (“SOx”) among other components. The CO produced during combustion of the spent catalyst can be further oxidized with the oxidant present therein to form CO₂.

The amount of oxygen introduced via the carrier fluid in line 130 can range from a low of about 0.5%, about 1%, about 3%, about 5%, or about 10% to a high of about 50%, about 55%, or about 60% of the total amount of oxygen introduced to the regenerator 140 via lines 130 and 119. In another example, the amount of oxygen introduced via the carrier fluid in line 130 can be about 15%, about 20%, or about 25% of the total amount of oxygen introduced via lines 130 and 119 to the regenerator 140. The amount of oxygen introduced via the fluid in line 119 can range from a low of about 40%, about 45%, or about 50% to a high of about 75%, about 85%, about 95%, or about 99.5% of the total amount of oxygen introduced to the regenerator 140 via line 130 and/or line 119. For example, the amount of oxygen introduced via line 119 can be about 75%, about 80%, or about 85% of the total amount of oxygen introduced via lines 130 and 119. The amount of oxygen introduced to the regenerator 140 via lines 119 and 130 can remain constant or can vary. The amount of oxygen introduced to the regenerator 140 via lines 119 and 130 can remain constant or can vary with respect to one another.

The cyclones 165 can separate at least a portion of any entrained catalyst and/or other particulates, such as non-combusted coke particles, in the flue gas to provide a solids-lean flue gas via line 166 and separated catalyst and other particulate matter via line 167. The cyclones 165 can provide catalyst separation efficiency greater than about 90%, about 95%, about 98%, about 99%, about 99.5%, about 99.9%, or about 99.99%. The separated catalyst and/or other particulates can be reintroduced to the dense phase catalyst zone 145 via lines 167. The solids-lean flue gas via line 166 can be introduced to plenum 168. The solids-lean flue gas via lines 166 from multiple cyclones 165 can be mixed within the plenum 168 and recovered as a flue gas via line 170 from the plenum 168.

In one or more embodiments, CO and/or coke afterburning can occur within the dilute phase catalyst zone 155, the cyclones 165, the plenum 168, and/or the flue gas recovery line 170. Afterburning of the CO and/or coke can increase the temperature of the flue gas recovered via line 170. For example, flue gas can enter the cyclones 165 at a temperature of about 670° C. to about to about 695° C. and due to afterburning of CO within the cyclones the flue gas exiting the cyclones 165 can be at a temperature of about 720° C. to about 765° C. However, the heat generated by the exothermic oxidation of the CO and/or coke can be acceptable, such that the flue gas temperature remains within catalyst regeneration system 100 operational limits. For example, the temperature of the flue gas with CO and/or coke afterburning can remain below about 900° C., below about 850° C., below about 800° C., below about 775° C., below about 760° C., or less.

The coke deposited on the spent catalyst introduced via nozzles 152 and/or CO produced during combustion of the coke can reduce the formation of NOx within the regenerator 140. For example, the coke deposited on the spent catalyst can reduce the formation of NOx within the dilute phase catalyst zone 155, thereby reducing the amount of NOx within the flue gas in line 170. Two potential or possible reaction pathways involving the carbon contained in coke on the spent catalyst and CO generated during combustion can include:

2NO+C→N₂+CO₂; and  (1)

2NO+2CO→N₂+2CO₂  (2)

The above potential or possible reactions, among others, can provide a flue gas having reduced NOx concentrations, which can be due, at least in part, to the increased amount of CO and/or carbon in the dilute phase catalyst zone 155. In one or more embodiments, the NOx concentration in the flue gas via line 170 can be less than about 150 ppm, less than about 100 ppm, less than about 75 ppm, less than about 50 ppm, less than about 40 ppm, less than about 30 ppm, less than about 20 ppm, about 15 ppm, or less. For example, the NOx concentration in the flue gas can range from about 15 ppm to about 45 ppm, about 15 ppm to about 27 ppm, about 25 ppm to about 40 ppm, or about 30 ppm to about 45 ppm.

The amount of oxidant via line 119 and/or in the carrier fluid via line 130 can range from a low of about 80%, about 85%, or about 90% to a high of about 105%, about 110%, about 115%, or more of the stoichiometric oxygen required to oxidize the total amount of carbon and/or CO introduced and/or produced within the regenerator 140. In one or more embodiments, 100% of the stoichiometric oxygen required for complete combustion and oxidation of the materials introduced to the regenerator 140 can be introduced via line 119 and/or line 130. Excess oxygen ranging from a low of about 0.1%, about 0.5%, or about 1% to a high of about 1.5%, about 2.5%, or about 3.5% more than the stoichiometric oxygen required to oxidize the total amount of carbon and/or CO introduced and/or produced within the regenerator 140 can be introduced via line 119 and/or line 130. Introducing excess oxygen to the regenerator 140 can provide a flue gas via line 170 that contains oxygen ranging from a low of about 0.1% mol, about 0.5% mol, or about 1% mol to a high of about 2% mol, about 3% mol, about 4% mol, or more. In at least one specific embodiment the oxygen content of the flue gas via line 170 can range from about 1.5% mol to about 2.5% mol.

The catalyst or catalyst particles can provide a heat sink within the regenerator 140. In other words, the catalyst particles can provide enough heat absorption to reduce the temperature within the regenerator 140 due to the combustion of coke and/or CO. The catalyst particles can provide enough heat absorption to prevent the temperature within the regenerator 140 from exceeding operational limits.

In one or more embodiments, the catalyst can include, but is not limited to, one or more zeolites, metal impregnated catalysts, faujasite zeolites, modified faujasite zeolites, Y-type zeolites, ultrastable Y-type zeolites (USY), rare earth exchanged Y-type zeolites (REY), rare earth exchanged ultrastable Y-type zeolites (REUSY), rare earth free Z-21, Socony Mobil #5 zeolite (ZSM-5), ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, or any other high activity zeolite catalysts.

FIG. 2 depicts a partial cross-sectional view of an illustrative catalyst regeneration system 200 having a spent catalyst distributor 150 and fluid introduction nozzles 205 disposed above a dense phase catalyst bed 145, according to one or more embodiments. The catalyst regeneration system 200 can be similar to the catalyst regeneration system 100 discussed and described above with reference to FIG. 1, and can further include one or more fluid introduction nozzles 205 disposed above the dense phase catalyst bed 145 within the regenerator 140. The catalyst regeneration system 200 can also include one or more CO promoter introduction lines 215 in fluid communication with the spent catalyst in line 131. The nozzles 205 can be disposed above the surface 149 of the dense phase catalyst bed 145. In one or more embodiments, a fluid via lines 203 can be introduced to one or more nozzles 205. The fluid introduced via line 203 can include, but is not limited to, air, oxygen-rich gas, oxygen-lean gas, ozone, CO, CO₂, nitrogen, steam, combustion or exhaust gas, or any combination thereof. In one or more embodiments, a fluid introduced via line 203 that includes an oxidant can further oxidize CO and/or coke therein. The amount of oxygen introduced via the fluid in line 203 can range from a low of about 0.5%, about 1%, about 3%, or about 5% to a high of about 20%, about 30%, about 40%, or about 50% of the total amount of oxygen introduced to the regenerator 140 via lines 130, 119, and 203. The amount of oxygen introduced via the carrier fluid in line 130 can range from a low of about 0.5%, about 1%, about 3%, or about 5% to a high of about 20%, about 30%, about 40%, or about 50% of the total amount of oxygen introduced to the regenerator 140 via lines 130, 119, and 203. The amount of oxygen introduced with the fluid via line 119 can range from a low of about 40%, about 45%, or about 50% to a high of about 75%, about 85%, or about 95% of the total amount of oxygen introduced to the regenerator 140 via lines 130, 119, and 203. The amount of oxygen introduced via the carrier fluid in line 130 and the fluid via line 203 can range from a low of about 0.5%, about 1%, about 3%, or about 5% to a high of about 20%, about 40%, about 60%, or about 70% of the total amount of oxygen introduced to the regenerator 140 via lines 130, 119, and 203. For example, the amount of oxygen introduced via lines 130 and 203 can be about 15%, about 20%, about 25%, about 30%, or about 35% of the total amount of oxygen introduced to the regenerator via lines 130, 119, and 203.

The one or more CO oxidation promoters via line 215 can be introduced directly to the mixture in line 135, the carrier fluid in line 130, and/or the spent catalyst in line 131. The CO oxidation promoter can reduce the temperature at which CO combusts within the regenerator 140, thereby converting CO to CO₂ at a lower temperature to provide a flue gas via line 170 containing little or no CO. For example, the CO concentration in the flue gas via line 170 can be less than about 2% mol, less than about 1.5% mol, less than about 1% mol. less than about 0.7% mol, less than about 0.5% mol, less than about 0.3% mol, less than about 0.1% mol, or less than about 0.01% mol.

The CO oxidation promoter can include, but is not limited to, platinum, palladium, iridium, rhodium, osmium, ruthenium, and rhenium, oxides thereof, derivatives therefore, or any combination thereof. In one or more embodiments, the CO oxidation promoter can be disposed on a support. Suitable supports can include, but are not limited to, silica, alumina, and silica-alumina. Examples of commercially available alumina supports are available under trade names such as PURALOX, CATAPAL and VERSAL. Examples of commercially available silica-alumina supports are available under trade names such as SIRAL and SIRALOX.

The CO oxidation promoter can be categorized based upon the amount of the CO oxidation promoter present within the regeneration system 200. For example, a low activity level CO oxidation promoter can be referred to as having a concentration of the active ingredient, e.g. platinum, within the regeneration system 200 ranging from greater than zero to a high of about 0.3 ppm. A medium activity level CO promoter can be referred to as having a concentration of the active ingredient, e.g. platinum, within the regeneration system 200 ranging from about 0.3 ppm to about 0.9 ppm. A high activity level CO promoter can be referred to as having a concentration of the active ingredient, e.g. platinum, within the regeneration system 200 ranging from a low of about 0.9 ppm to a high of about 2 ppm. A high activity level CO promoter can be present at a concentration greater than 2 ppm, for example about 2.5 ppm, about 3 ppm, or about 4 ppm.

The presence of a CO oxidation promoter can reduce the temperature at which CO will burn, which can reduce the temperature of the flue gas as more of the CO will burn in the dense phase catalyst zone 145 rather than in the dilute phase catalyst zone 155. The reduction in the CO combustion temperature can prevent or reduce a temperature rise within the regenerator 140 and in particular the dilute phase catalyst zone 155 from exceeding operationally safe limits. The temperature within the regenerator 140 and in particular the dilute phase catalyst zone 155 can be maintained below about 900° C., below about 850° C., below about 800° C., below about 775° C., below about 760° C., or less.

In one or more embodiments, the presence of a CO oxidation promoter can promote the combustion of CO within the dense phase catalyst bed 145. The combustion of at least a portion of the CO within the dense phase catalyst bed 145 can reduce the amount of CO combusted within the dilute phase catalyst bed 155, where a higher temperature is more likely or probable, due to the presence of less catalyst particles and therefore, less heat sink.

In one or more embodiments, fresh or “make-up” catalyst can be added via line 210 to the regenerator 140. The make-up catalyst can be introduced to maintain a predetermined amount of catalyst within the catalyst regeneration system 200. The introduction of make-up catalyst via line 210 can be introduced to the spent catalyst in line 131, the spent catalyst mixture in line 135, the regenerator 140, the regenerated catalyst in line 177 or any other suitable location within the catalyst regeneration system 200.

FIG. 3 depicts a partial cross-sectional view of the illustrative catalyst regeneration system 100 depicted in FIG. 1, further including an illustrative variable oxygen content carrier fluid generation system 300, according to one or more embodiments. The variable oxygen content carrier fluid generation system (“carrier fluid system”) 300 can include, but is not limited to, one or more turbines 105, one or more blowers 115, and one or more heaters 125.

The turbine 105 can provide a combustion gas or exhaust gas via line 109. In one or more embodiments, the blower can provide compressed via line 117. The gas introduced to the blower 115 via line 111 can include, but is not limited to, air, oxygen-rich gas, oxygen-lean gas, CO, CO₂, or any combination thereof. In one or more embodiments, the combination of the turbine 105, blower 115, and/or heater 125 can be operated to provide a carrier gas via line 130 ranging from an oxygen-lean gas to an oxygen-rich gas via line 130 having a predetermined temperature, pressure, and velocity. The turbine 105, blower 115, and/or heater 125 can be replaced with any system suitable for providing a carrier gas via line 109 ranging from an oxygen-lean gas to an oxygen-rich gas. In one or more embodiments, steam via line 129 can be introduced to the combustion gas 109, the compressed gas in line 127, or a mixture thereof to provide a carrier gas via line 130 that includes steam. In one example, steam via line 129 can be introduced as the carrier fluid via line 130. As illustrated, the fluid in line 119 can be provided by the blower 115. Although not shown, the fluid in line 119 can be pre-heated prior to introduction to the regenerator 140 via the nozzles 160.

The turbine 105 can be any turbine suitable for generating power. For example, the turbine 105 can be a gas turbine in which a fuel and an oxidant can be combusted in a combustor and compressed upstream of the turbine. The compressed combusted gas can then be introduced to the gas turbine to generate power in one or more generators (not shown) and to provide a hot gas or exhaust gas via line 107. Another suitable type of turbine can be a combustion turbine where the combustion of the fuel can be integrated within the turbine (i.e. the combustion of the fuel occurs within the turbine). The fuel can be any suitable fuel, such as syngas, hydrogen, methane, other combustible fuel, or mixtures thereof. In one or more embodiments, a fuel via line 102 and an oxidant via line 104 can be introduced to the turbine 105 which can be combusted to provide the exhaust gas via line 107 and power to drive the blower 115.

The blower 115 can be any blower suitable for providing a compressed gas via line 117. In at least one specific embodiment, the blower 115 can be independently driven, i.e. the blower can be powered by equipment other than the turbine 105.

The heater 125 can include any system, device, or combination of systems and/or devices suitable for heating a fluid. In one or more embodiments, the fluid via line 117 can be indirectly heated within the heater 125. In one or more embodiments, the fluid via line 117 can be directly heated within the heater 125, for example by mixing with the combustion products provided by the combustion of a fuel introduced via line 121.

In one or more embodiments, other equipment that can be used to provide a variable oxygen content carrier fluid can include, but is not limited to, one or more air separation units, which can provide an oxygen-rich gas, other combustion systems, or the like. The air separation unit can include cryogenic distillation, pressure swing adsorption, membrane separation, or any combination thereof.

FIG. 4 depicts a partial cross-sectional view of an illustrative catalyst regeneration system 400 having a spent catalyst introduction line in 305 fluid communication with a dense phase catalyst bed 145 and one or more fluid introduction nozzles 405 disposed above the dense phase catalyst bed 145, according to one or more embodiments. Referring to both FIGS. 3 and 4, the catalyst regeneration systems 300, 400 can include one or more regenerators 140, one or more turbines 105, one or more blowers 115, and/or one or more heaters 125, which can be the same as those discussed and described above with reference to FIG. 1. Similar as discussed and described above with reference to FIG. 1, the regenerator 140 can include a dense phase catalyst zone 145, a dilute phase catalyst zone 155, one or more fluid introduction nozzles (two are shown 160), one or more cyclones (two are shown 165), one or more plenums 167, one or more flue gas recovery lines 170, and one or more regenerated catalyst recovery outlets 175. The catalyst regeneration system 400 can further include one or more nozzles 405 disposed above the surface 149 of the dense phase catalyst bed 145.

A carrier fluid via line 130 and spent catalyst via line 131 can be introduced to line 305 to provide a mixture of spent catalyst and carrier fluid. In one or more embodiments, line 305 can be in fluid communication with the dense phase catalyst zone 145. In one or more embodiments, the spent catalyst and carrier fluid via line 305 can be introduced to the first zone 146 of the dense phase catalyst zone 145. In one or more embodiments, the spent catalyst and carrier fluid via line 305 can be introduced to the second zone 147 of the dense phase catalyst zone 145. In one or more embodiments, the spent catalyst and carrier fluid via line 305 can be introduced to the third zone 148 of the dense phase catalyst zone 145. In one or more embodiments, the spent catalyst and carrier fluid via line 305 can be introduced to the first zone 146, the second zone 147, the third zone 148, or any combination thereof. The carrier fluid introduced via line 130 can be any suitable carrier fluid. Similar as discussed and described above with reference to FIG. 1, the carrier fluid in line 130 can include a gas ranging from oxygen-lean to oxygen-rich.

A gas or fluid containing an oxidant, e.g. oxygen gas, introduced via line 119 to the nozzles 160, an oxidant present in the carrier gas introduced via line 130, and/or an oxidant introduced via the nozzles 405 can combust or oxidize the coke deposited on the catalyst introduced via line 131 to provide a flue gas via line 170 and a regenerated catalyst via line 177, as discussed and described above with reference to FIGS. 1-3. The fluid introduced via line 119 to the nozzles 160 can introduce enough fluid velocity within the dense phase catalyst bed 145 to provide a fluidized catalyst bed 145.

A fluid via line 403 can be introduced to the one or more nozzles 405 disposed within the regenerator 140 of the catalyst regeneration system 400. Illustrative fluids can include, but are not limited to, air, oxygen-rich gas, oxygen-lean gas, ozone, steam, CO, CO₂, nitrogen, exhaust or combustion gas, or any combination thereof. The catalyst regeneration system 400 can also include a CO oxidation promoter introduction line 215 and/or make-up catalyst introduction line 210, as discussed and described above with reference to FIG. 2.

The amount of oxygen introduced via the fluid in line 403 can range from a low of about 3%, about 5%, about 7%, or about 9% to a high of about 20%, about 30%, about 40%, or about 50% of the total amount of oxygen introduced to the regenerator 140 via lines 130, 119, and 403.

FIG. 5 depicts a partial cross-sectional top view of an illustrative catalyst regenerator 140, according to one or more embodiments. FIG. 5 illustrates one exemplary configuration of the cyclones 165 and fluid introduction nozzles 160 disposed within the regenerator 140. As illustrated in FIG. 5, the distributor 150, lines 135, 210, or 305, and the fluid introduction nozzles 205, which are shown in FIGS. 1, 2, 3, and/or 4, are left out for clarity.

A plurality of fluid introduction nozzles 160 can be distributed about a lower portion of the regenerator 140. As shown, nine fluid introduction nozzles 160 are shown distributed about the regenerator 140. Also shown, are four cyclones 165 disposed within the regenerator 140. Any number of fluid introduction nozzles 160 and any number of cyclones 165 can be disposed within the regenerator 140. The number and particular placement of the fluid introduction nozzles 160 and cyclone 165 can be determined, at least in part, based on the particular catalyst regeneration system 100, 200, 300, and 400 operational requirements.

The flue gas and entrained particulates, such as catalyst particles, can enter the cyclones via cyclone inlet 505. The cyclones can then separate solids or particulates from the flue gas to provide a solids-lean flue gas. The solids-lean flue gas can be recovered via line 170 and the particulates can be returned to the dense phase catalyst zone 145, as discussed and described above with reference to FIGS. 1-4.

FIG. 6 depicts an illustrative fluid catalytic cracking system 600, according to one or more embodiments. The FCC system 600 can include a fluidized catalytic cracker (“FCC”) 603 or any other suitable system having one or more risers 605, ducts 610, separation zones 615, and regenerators 140. The regenerator 140 can be similar to the regenerators 140 discussed and described above with reference to FIGS. 1-5. In one or more embodiments, the system 600 can further include a gas turbine 105, a blower 115, and an air heaters 125, which can be similar as discussed and described above with reference to FIGS. 1-4. In one or more embodiments, steam via line 630, one or more hydrocarbons via line 635, and one or more catalysts via line 177 can be introduced to the one or more risers 605, forming a fluidized mixture (“reaction mixture”) therein. The steam via line 630 and the catalyst via line 177 can be fed separately to the riser 605 as shown in FIG. 6, or the steam and the catalyst can be mixed and fed together as a mixture to the riser 605.

Heat in the riser 605 provided by the steam via line 630 and the catalyst via line 170 can vaporize the hydrocarbon feed via line 635 entering the riser via line 605, to provide the reaction mixture therein. Supplemental heat and/or firing can be provided to the one or more risers 605 using waste heat (not shown) provided from the regenerator 140. Within the riser 605, the hydrocarbons within the reaction mixture can be cracked into one or more hydrocarbons and hydrocarbon by-products to provide a first product mixture. At least a portion of the hydrocarbon by-products present in the riser 605 can deposit on the surface of the catalyst particles, forming coked-catalyst particles or spent catalyst. Thus, the first product mixture exiting the riser 605 can contain coked-catalyst particles suspended in gaseous hydrocarbons, hydrocarbon by-products, coke dust or particulates, steam, and other inerts.

The amount of coke or carbon deposited on the catalyst particles can range from about 0.01% wt to about 5% wt, about 0.1% wt to about 4% wt, or about 0.15% wt to about 3% wt. For example, the amount of coke or carbon deposited on the catalyst particles can range from a low of about 0.01% wt, about 0.1% wt, or about 0.5% wt to a high of about 1% wt, about 1.2% wt, or about 1.4% wt. In another example, the amount of coke deposited on the catalyst particles can range from about 0.5% wt to about 1.5% wt, from about 0.7% wt to about 1.1% wt, or from about 0.9% wt to about 1.2% wt. In at least one specific embodiment, the amount of coke deposited on the catalyst particles can be about 1% wt.

In one or more embodiments, the catalyst-to-hydrocarbon weight ratio can range from about 4:1 to about 8:1; from about 4.5:1 to about 7.5:1; or from about 5:1 to about 7:1. In one or more embodiments, the riser 605 can be operated at a temperature ranging from a low of about 475° C., about 490° C., or about 500° C. to a high of about 550° C., about 600° C., or about 650° C. For example, the riser 605 can be operated at a temperature ranging from about 500° C. to about 595° C., from about 505° C. to about 585° C., or from about 510° C. to about 565° C.

The velocity of the reaction mixture flowing through the riser 605 can range from about 3 m/sec to about 27 m/sec, about 6 m/sec to about 25 m/sec, or about 9 m/sec to about 21 m/sec. The residence time of the reaction mixture in the riser 605 can be less than about 20 seconds, less than about 10 seconds, less than about 8 seconds, less than about 4 seconds, or less than about 2 seconds.

The first product mixture can flow, via the duct (or transition line) 610, to the one or more separation zones 615 where the coked-catalyst particles and/or other particulates can be separated from the gaseous hydrocarbons, steam, and inerts. The separation zone 615 can have a larger cross-sectional area than either the riser 605 or the duct 610 to reduce the velocity of the gas, allowing the heavier coked-catalyst particles and/or other particulates to separate from the gaseous hydrocarbons, steam, and inerts. In one or more embodiments, a steam purge (not shown) can be added the separation zone 615 to assist in separating the gaseous hydrocarbons from the coked-catalyst particles, i.e. stripping the gaseous hydrocarbons from the solids.

The gaseous hydrocarbons (“first product”) via line 650 can be recovered from the separation zone 615. Although not shown, in one or more embodiments, the first product in line 650 can be further processed, such as by dehydrating or fractionating to provide one or more finished products including, but not limited to, one or more olefins, paraffins, aromatics, mixtures thereof, derivatives thereof, and/or combinations thereof. The solids, i.e. coked-catalyst particles, can free fall through the separation zone discharge 131 toward the regenerator 140.

Within the regenerator 140, the coked-catalyst particles and carrier fluid mixture via line 135 can be combined with the fluid introduced via line 119 to provide the flue gas via line 170 and regenerated catalyst via line 177, as discussed and described above with reference to FIGS. 1-5.

The flue gas in line 170 can be introduced to one or more optional CO boilers (not shown) to remove additional CO. The one or more CO boilers can be any type of CO boiler, which are well-known. The CO boiler can be operated in multiple stages to reduce the flame temperature occurring in any one stage and limit NOx formation in an oxidizing atmosphere. Low NOx burners can also be used to burn the fuel gas (not shown) which may be needed to keep the CO boiler lit.

The cleaned flue gas via line 170 introduced to one or more optional CO boilers can contain very little that will burn. Most or all of the NOx and NOx precursors in the flue gas can be eliminated within the regenerator 140 where most or all the CO in the flue gas can be eliminated as well. The flue gas in line 170 can have a heating value of less than about 7,500 kJ/m³, less than about 3,700 kJ/m³, less than about 2,800 kJ/m³, less than about 1,900 kJ/m³, less than about 950 kJ/m³, or less than about 400 kJ/m³.

In one or more embodiments, ammonia or an ammonia precursor such as urea can be introduced (not shown) to the optional CO boiler (not shown) to reduce NOx emissions even further. These materials can react quickly with NOx and NOx precursors to reduce it to nitrogen. Additional details for conventional FCC processes and flue gas treatment can be found in U.S. Pat. Nos. 5,268,089; 4,514,285; and 5,773,378; which are incorporated by reference herein.

In one or more embodiments, at least a portion of the flue gas via line 170 and/or flue gas from the one or more optional CO boilers can be vented to the atmosphere and/or sent to a heat recovery unit (not shown) and then vented to the atmosphere, sequestered under ground, or otherwise disposed. The one or more optional CO boilers, if used can reduce the CO content of the flue gas in line 170 by about 50%, about 70%, about 80%, about 90%, about 95%, about 98%, about 99%, about 99.5%, about 99.9%, or about 99.99%. In one or more embodiments, the one or more optional CO boilers can reduce the CO content of the flue gas in line 170 by from about 50% to about 99%; from about 95% to about 99.99%; from about 97% to about 99.9%; or from about 99% to about 99.99%.

Although not shown, in one or more embodiments, a carbon dioxide (CO₂) separation unit can be used to remove at least a portion of the CO₂ from the flue gas in line 170. In one or more embodiments, CO₂ can be removed for sequestration or reuse, e.g., reuse through enhanced oil recovery.

In one or more embodiments, the one or more optional heat recovery units (not shown) can include any device, system or combination of systems and/or devices suitable for transferring heat from a fluid at a higher temperature to a fluid at a lower temperature. In one or more embodiments, the heat recovery unit can include, but is not limited to single or multiple pass heat exchange devices such as shell and tube heat exchangers, plate and frame heat exchangers, spiral heat exchangers, bayonet type heat exchangers, U-tube heat exchangers, and/or any similar system or device.

Within the regenerator 140 a fluidized mixture, containing spent catalyst particles, regenerated catalyst particles, oxidants, carbon monoxide, carbon dioxide, nitrogen oxides, and/or the one or more fluids introduced via line 119 can be combined within the regenerator 140 with one or more optional doping agents introduced via line 675. The dispersal and deposition of the one or more doping agents on the regenerated catalyst can be enhanced by the high temperature and/or turbulence present in the regenerator 140.

Supplemental fuel, for example natural gas, can be introduced to the regenerator 140 via line 675. The use of supplemental fuel can provide additional heat within the regenerator 140, further enhancing the regeneration of the coked-catalyst particles therein.

Turbulence within the regenerator 140 can improve the even dispersion of the one or more doping agents within the fluidized catalyst zone 145, increasing the contact between the one or more doping agents with the reactive surfaces on the regenerated catalyst. In contrast, the one or more doping agents in a traditional, homogeneously doped, catalyst are dispersed within the catalyst particles. Consequently, less doping agent can be used to achieve the same concentration of doping agent on the surface of the regenerated catalyst particle. Also, changing doping agents in response to changing process conditions and/or hydrocarbon feed composition can be more readily achieved since little or no entrained doping agent exists within the catalyst particle, i.e. the interior matrix of the catalyst particle. For example, the doping agent can be changed simply by changing the type and/or composition of the doping agent added to the regenerator 140.

The selection of an appropriate doping agent or additive or blend of two or more doping agents or additives can be based upon the composition of the incoming hydrocarbon feed via line 635, and/or desired gaseous hydrocarbons in the first product exiting the separation zone 615 via line 650. For example, the addition of a class 2 doping agent such as magnesium or barium can preferentially increase the production of ethylene in the first product in line 650. The addition of a class 13 doping agent such as gallium can result in the increased production of aromatic hydrocarbons in the first product in line 650. The addition of class 8, 9, or 10 doping agents such as ruthenium, rhodium or palladium can preferentially increase the production of propylene in the first product in line 650.

Doped catalyst particles and/or regenerated catalyst particles with or without one or more doping agents or additives can be recycled to the one or more risers 605 via line 177. In one or more embodiments, the flow of regenerated catalyst from the regenerator 140 can be controlled using one or more valves (not shown), which can be manually or automatically adjusted or controlled based upon parameters derived from process temperatures, pressures, flows and/or other process conditions. In one or more embodiments, at least 90% wt, at least 95% wt, at least 99% wt, at least 99.99% wt, at least 99.9975% wt, or at least 99.999% wt of the total catalyst and/or doped catalyst originally introduced to the riser 605 via line 177 can be regenerated, optionally doped with one or more doping agents, and recycled back to the riser 605.

The hydrocarbon feed in line 635 can include any suitable hydrocarbon or mixture of hydrocarbons. For example, the hydrocarbon feed in line 635 can include, but is not limited to, naphtha, gas oils, deasphalted oils, recycle gas oils, coker gas oils, vacuum gas oils, vacuum residua, Atmospheric residua. The hydrocarbon feed in line 635 can include any combination of C₂ to C₄₀₊ hydrocarbons. For example, the hydrocarbon feed in line 635 can include C₅ to C₁₁, C₁₁ to C₁₉, C₁₆ to C₂₅, C₁₆ to C₄₀, C₂₀ to C₄₀, C₄₀ to C₁₀₀ hydrocarbons or any combination or mixture thereof. The hydrocarbon feed in line 635 can include, but is not limited to, olefins, paraffins, naphthenes, and/or mixtures thereof. In one or more embodiments, the hydrocarbon feed can originate from a refinery. For example, the hydrocarbon feed can be a gas mixture resulting from the distillation of crude oil. In one or more embodiments, the hydrocarbon feed in line 635 can include at least 60% wt C₂-C₁₁ olefins and paraffins.

The hydrocarbon feed introduced via line 635 can be pre-heated (not shown) prior to introduction to the riser 605. Although not shown in FIG. 6, a regenerative heat exchanger using waste process heat can be used to pre-heat the hydrocarbon feed. The temperature of the hydrocarbon feed can range from about 175° C. to about 375° C., about 225° C. to about 350° C., or about 250° C. to about 325° C. The pressure of the hydrocarbon feed can range from about 100 kPa to about 3,450 kPa, about 100 kPa to about 2,750 kPa, or about 100 kPa to about 350 kPa.

The hydrocarbon feed introduced via line 635 can be partially or completely vaporized prior to introduction to the one or more risers 605. The hydrocarbon feed can be about 10% vol to about 100% vol; about 20% vol to about 60% vol; about 30% vol to about 60% vol; about 40% vol to about 60% vol; or about 50% vol to about 60% vol vaporized. In one or more embodiments, the hydrocarbon feed can be at least about 70% vol to about 100% vol; about 80% vol to about 100% vol; or about 90% vol to about 100% vol vaporized. The hydrocarbon feed can be a minimum of 80% wt vaporized; 85% wt vaporized; 90% wt vaporized; 95% wt vaporized; or about 99% wt vaporized prior to introduction to the riser 605. Within the riser 605, the pressure and temperature can be adjusted either manually or automatically to compensate for variations in hydrocarbon feed composition and to maximize the yield of preferred hydrocarbons obtained by cracking the hydrocarbon feed in the presence of the one or more doped catalysts.

In one or more embodiments, the steam introduced via line 630 to the one or more risers 605 can be saturated. The pressure of the saturated steam can be a minimum of about 1,000 kPa, about 2,000 kPa, about 4,000 kPa, or about 6,000 kPa. In one or more embodiments, the pressure of the saturated steam can range from about 100 kPa to about 8,300 kPa; about 100 kPa to about 4,000 kPa; or about 100 kPa to about 2,000 kPa.

In one or more embodiments, the steam introduced via line 630 to the one or more risers 605 can be superheated. In one or more embodiments, where superheated steam is used, the pressure of the superheated steam can be a minimum of about 1,000 kPa, about 2,000 kPa, about 4,000 kPa, or about 6,000 kPa. In one or more embodiments, the pressure of the superheated steam can range from about 100 kPa to about 8,300 kPa; about 100 kPa to about 4,000 kPa; or about 100 kPa to about 2,000 kPa. In one or more embodiments, the temperature of the superheated steam can be a minimum of about 200° C., about 230° C., about 260° C., or about 290° C.

The steam can be introduced via line 630 to the riser 605 at a rate proportionate to the hydrocarbon feed rate via line 635. The steam-to-hydrocarbon feed weight ratio can range from about 1:20 to about 50:1; from about 1:20 to about 20:1; or from about 1:10 to about 20:1.

The first product in line 650 can include from about 5% wt to about 30% wt C₂; about 5% wt to about 60% wt C₃; about 5% wt to about 40% wt C₄; about 5% wt to about 50% wt C₅, and heavier hydrocarbons. The temperature of the first product in line 650 can range from about 425° C. to about 815° C.; about 450° C. to about 760° C.; or about 480° C. to about 730° C.

Although not shown, the separation zone 615 can be disposed above (not shown) the riser 605. In one or more embodiments, the separation zone 615 can include a separation zone discharge (not shown), which can provide fluid communication between the separation zone 615 and regenerator 140. The separation zone discharge 615 can include one or more valves to manually or automatically adjust or control the flow of spent catalyst to the regenerator 140 based on parameters derived from process temperatures, pressures, flows, and/or other process conditions.

Prophetic Examples

Embodiments of the present invention can be further described with the following simulated processes. The following simulated process results are based on a mathematical model simulating both combustion kinetics and fluid bed hydrodynamics. Tables 1-6 illustrate a base case and a base case modified according to embodiments discussed and described herein. Table 1 shows simulated process results for a base case A in which a distributor 150 is positioned within the lower portion or first zone 146 of the dense phase catalyst zone 145 (note that the configuration for base case A is not depicted in FIGS. 1-6). Therefore, the spent catalyst and carrier fluid mixture for base case A is introduced to the lower zone 146. Modified case A, in contrast, places the distributor 150 above the surface 149 of the dense phase catalyst zone 145, thereby introducing the spent catalyst/carrier fluid mixture above the surface 149 of the dense phase catalyst zone 145 and into the upper or transitional zone 148, as discussed and described above with reference to FIG. 1. For Tables 1-3 the carrier fluid introduced via line 129 is air. No CO promoter is used in either the base case A or the modified case A. It should be noted that for every case, i.e. base cases A-C and modified cases A-C shown in Tables 1-3, the coke burning rate remains the same with 5,350 kg/hr of coke burned.

TABLE 1 Base Modified Case A Case A Carrier Fluid Introduced via Line 129 Air Air Spent Catalyst Inlet Temperature, ° C. 537 537 Regenerated Catalyst Outlet Temperature, ° C. 712 706 Carbon Content (wt %) on Regenerated Catalyst 0.03 0.05 Carbon Content (wt %) on Spent Catalyst 0.78 0.80 Coke Burning Rate, kg/hr 5348 5348 Total Catalyst Inventory, kg 73.8 80.8 Lower Temperature, ° C. 702 706 Zone 146 of Density, kg/m³ 410 455 Fluidized Superficial Gas Velocity, m/s 0.82 0.53 Catalyst Bed wt % Carbon in Catalyst Bed 0.06 0.05 Conditions CO % mol leaving First Zone 1.28 1.02 NOx ppm leaving First Zone 66.5 78.4 O₂ % mol leaving First Zone 8.94 6.58 Coke Burning Rate, kg/hr 3626 2788 Catalyst Inventory, tonnes 20.0 22.1 Middle Temperature, ° C. 712 697 Zone 147 of Density, kg/m³ 402 450 Fluidized Superficial Gas Velocity, m/s 0.89 0.56 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.09 Conditions CO % mol leaving Catalyst Bed 0.65 2.04 NOx ppm leaving Second Zone 82.5 1.5 O₂ % mol leaving Second Zone 3.07 0.2 Coke Burning Rate, kg/hr 1495 1280 Catalyst Inventory, tonnes 40.6 45.4 Upper Temperature, ° C. 713 641 Zone 148 of Density, kg/m³ 399 150 Fluidized Superficial Gas Velocity, m/s 0.93 0.86 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.32 Conditions CO % mol leaving Third Zone 0.64 1.64 NOx ppm leaving Third Zone 81.5 10.5 O₂ % mol leaving Third Zone 2.94 6.75 Coke Burning Rate, kg/hr 91 183 Catalyst Inventory, tonnes 1.43 1.45 Dilute Phase Carbon Content (wt %) 0.01 0.19 Zone 155 CO % mol leaving Dilute Phase 0.03 1.24 Zone NOx ppm leaving Dilute Phase 165 16 Zone O₂ % mol leaving Dilute Phase 2.14 2.73 Zone Coke Burning Rate, kg/hr 136 1097 Cyclone 165 Cyclone Inlet Temperature, ° C. 718 678 Cyclone Outlet Temperature, ° C. 721 778 Cyclone Catalyst Loading, 14.0 13.3 tonnes/min Flue Gas CO % mol 0 0 Composition NOx ppm 165 16 via line 170 O₂% mol 2.12 2.12

As shown in Table 1, base case A provides a flue gas via line 170 that contains 165 ppm NOx, while the modified case A provides a flue gas via line 170 that contains 15.7 ppm. With the exception of the lower zone 146 the amount of NOx within the regenerator 140 for the modified case A is less than for the base case A. For example, the NOx concentration in the middle zone 147 in the modified case A is 1.5 ppm NOx versus 82.5 ppm NOx for the base case A and for the NOx concentration in the upper zone 148 in the modified case A is 10.5 ppm NOx versus 81.5 ppm NOx for the base case A.

As shown in Table 1, the CO and carbon present within the regenerator 140 in the middle zone 147, upper zone 148, and dilute phase catalyst zone 155 increased for the modified case A. The increase in CO and carbon within these zones increases the amount of NOx that can be converted to N₂ within the regenerator 140, thereby providing a flue gas via line 170 having a reduced NOx content. As illustrated in Table 1, the flue gas via line 170 for the modified case A contains about 90.5% less NOx than in base case A (165 ppm NOx for the base case A compared to 15.7 ppm NOx for the modified case A).

As shown in Table 1, the temperature of the flue gas at the cyclone 165 inlet for base case A is 718° C., while the temperature of the flue gas at the cyclone 165 outlet is 721° C., which is only a 3° C. temperature difference. However, for the modified case A the temperature of the flue gas at the cyclone 165 inlet is 678° C. and the temperature of the flue gas at the cyclone 165 outlet is 778° C., a 100° C. difference. This increased temperature difference for the modified case A is attributed to afterburning of the CO within the cyclone 165, as discussed and described above with reference to FIG. 1. The increase in temperature within the cyclones 165 and the flue gas via line 170 remains within operationally acceptable ranges, while providing a flue gas having reduced NOx concentrations.

Table 2 shows simulated process results for a base case B and a modified case B, which are both the same as discussed above with reference to Table 1, except a medium activity level CO promoter has been introduced to the catalyst regeneration system for both the base case B and the modified case B, as discussed and described above with reference to FIG. 2. For these simulated results the medium activity level CO promoter was platinum at a concentration of 0.7 ppm in the catalyst regeneration system.

TABLE 2 Base Modified Case B Case B Carrier Fluid Introduced via Line 129 Air Air Spent Catalyst Inlet Temperature, ° C. 537 537 Regenerated Catalyst Outlet Temperature, ° C. 712 707 Carbon Content (wt %) on Regenerated Catalyst 0.03 0.05 Carbon Content (wt %) on Spent Catalyst 0.78 0.8 Coke Burning Rate, kg/hr 5348 5348 Total Catalyst Inventory, tonnes 73.8 80.7 Lower Temperature, ° C. 703 707 Zone 146 of Density, kg/m³ 408 455 Fluidized Superficial Gas Velocity, m/s 0.82 0.53 Catalyst Bed wt % Carbon in Catalyst Bed 0.06 0.05 Conditions CO % mol leaving First Zone 0.91 0.82 NOx ppm leaving First Zone 91.1 85.2 O₂ % mol leaving First Zone 8.73 5.26 Coke Burning Rate, kg/hr 3399 2992 Catalyst Inventory, tonnes 20 22.1 Middle Temperature, ° C. 712 697 Zone 147 of Density, kg/m³ 402 449 Fluidized Superficial Gas Velocity, m/s 0.89 0.56 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.1 Conditions CO % mol leaving Catalyst Bed 0.49 1.56 NOx ppm leaving Second Zone 107 1.1 O₂ % mol leaving Second Zone 2.99 0.1 Coke Burning Rate, kg/hr 1768 1042 Catalyst Inventory, tonnes 40.6 45.3 Upper Temperature, ° C. 713 642 Zone 148 of Density, kg/m³ 397 150 Fluidized Superficial Gas Velocity, m/s 0.93 0.86 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.33 Conditions CO % mol leaving Third Zone 0.48 1.31 NOx ppm leaving Third Zone 106 12.9 O₂ % mol leaving Third Zone 2.86 6.67 Coke Burning Rate, kg/hr 45 181 Catalyst Inventory, tonnes 1.43 1.45 Dilute Phase Carbon Content (wt %) 0.015 0.197 Zone 155 CO % mol leaving Dilute Phase 0.03 1.05 Zone NOx ppm leaving Dilute Phase 185 18 Zone O₂ % mol leaving Dilute Phase 2.14 2.64 Zone Coke Burning Rate, kg/hr 136 1133 Cyclone 165 Cyclone Inlet Temperature, ° C. 717 678 Cyclone Outlet Temperature, ° C. 719 762 Cyclone Catalyst Loading, 14.0 13.3 tonnes/min Flue Gas CO % mol 0 0 Composition NOx ppm 186 18 via line 170 O₂ % mol 2.12 2.12

Table 2 shows similar results as Table 1, however the NOx concentration in the flue gas via line 170 is slightly higher for both the base case B and the modified case B, which is 186 ppm NOx and 17.9 ppm NOx, respectively. This result is expected because the presence of the medium activity CO promoter results in more complete combustion of the CO and, therefore, less CO is present within the regenerator that can react with the NOx to provide CO₂ and N₂. However, the increase in NOx for the modified case B is only slight, i.e. 2.2 ppm NOx, over the modified base case A.

The use of the medium activity level CO promoter also results in less CO afterburning for the modified case B than in the modified case A. This reduction in CO afterburning can be seen by the reduction in the temperature rise of the flue gas between the inlet and outlet of the cyclone 165. Specifically, the flue gas enters the cyclone 165 at a temperature of 678° C. and exits the cyclone 165 at a temperature of 762° C. Therefore, the modified case B provides a flue gas via line 170 having a temperature of 16° C. less than the flue gas provided in modified case A.

Table 3 shows simulated process results for a base case C and a modified case C, which are both the same as in Table 1, except a high activity CO promoter has been introduced to the catalyst regeneration system for both the base case C and the modified case C, as discussed and described above with reference to FIG. 2. For these simulated results the high activity level CO promoter was platinum at a concentration of 1.5 ppm in the catalyst regeneration system.

TABLE 3 Base Modified Case C Case C Carrier fluid introduced via line 129 Air Air Catalyst Regeneration Temperature, ° C. 712 711 Carbon Content (wt %) on Regenerated Catalyst 0.03 0.07 Carbon Content (wt %) on Spent Catalyst 0.78 0.81 Coke Burning Rate, kg/hr 5348 5348 Total Catalyst Inventory, tonnes 73.8 80.7 First Temperature, ° C. 703 711 Zone 146 of Density, kg/m³ 408 455 Fluidized Superficial Gas Velocity, m/s 0.82 0.54 Catalyst Bed wt % Carbon in Catalyst Bed 0.06 0.07 Conditions CO % mol leaving First Zone 0.43 0.45 NOx ppm leaving First Zone 184 117 O₂ % mol leaving First Zone 8.46 3.56 Coke Burning Rate, kg/hr 3399 3263 Catalyst Inventory, tonnes 20 22.1 Second Temperature, ° C. 712 699 Zone 147 of Density, kg/m³ 402 449 Fluidized Superficial Gas Velocity, m/s 0.88 0.57 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.12 Conditions CO % mol leaving Catalyst Bed 0.25 0.81 NOx ppm leaving Second Zone 204 0.8 O₂ % mol leaving Second Zone 2.87 0.03 Coke Burning Rate, kg/hr 1768 680 Catalyst Inventory, tonnes 40.6 45.3 Third Temperature, ° C. 713 643 Zone 148 of Density, kg/m³ 397 150 Fluidized Superficial Gas Velocity, m/s 0.93 0.86 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.34 Conditions CO % mol leaving Third Zone 0.24 0.79 NOx ppm leaving Third Zone 199 21 O₂ % mol leaving Third Zone 2.75 6.58 Coke Burning Rate, kg/hr 45 227 Catalyst Inventory, tonnes 1.43 1.45 Dilute Phase Carbon Content (wt %) 0.02 0.2 Zone 155 CO % mol leaving Dilute Phase 0.31 1.05 Zone NOx ppm leaving Dilute Phase 263 27 Zone O₂ % mol leaving Dilute Phase 2.12 2.44 Zone Coke Burning Rate, kg/hr 136 1178 Cyclone 165 Cyclone Inlet Temperature, ° C. 715 681 Cyclone Outlet Temperature, ° C. 718 733 Cyclone Catalyst Loading, 14.0 13.3 tonnes/min Flue Gas NOx ppm 263 27 Composition CO % mol 0 0 via line 170 O₂ % mol 2.12 2.12

Table 3 shows similar results as Tables 1 and 2, however the NOx concentration in the flue gas via line 170 is higher for both the base case C and the modified case C, which is 263 ppm NOx and 26.8 ppm NOx, respectively. Again this result is expected because the presence of the high activity CO promoter results in a further combustion of the CO and a further reduction in CO afterburning than in the base cases A and B and the modified cases A and B. The further reduction of CO afterburning can be seen by the further decrease in the temperature rise of the flue gas between inlet and outlet of the cyclone 165. Specifically, the flue gas enters the cyclone 165 at a temperature of 681° C. and exits the cyclone 165 at a temperature of 733° C. Therefore, the modified case C provides a flue gas via line 170 having a temperature 45° C. less than the flue gas provided in modified case A and 29° C. less than the flue gas provided in modified case B.

The increase in NOx in the flue gas for the modified case C still results in a flue gas in line 170 having a reduced NOx concentration versus the base case C (26.8 ppm NOx versus 263 ppm NOx). Furthermore, the increase in NOx in the flue gas for the modified case C still results in a flue gas in line 170 having a reduced NOx concentration versus the base case A which did not use a CO promoter (26.8 ppm NOx versus 165 ppm NOx).

Table 4 shows various operating and other simulation conditions used for the determination of the simulated results.

TABLE 4 Base Modified Cases A-C Cases A-C Geometries Bed Level, m 6.49 6.49 Bed Diameter of Bottom 5.49 5.49 Section, m Top Section Heights, m 8.96 8.96 Top Section Diameter, m 5.49 5.49 Conditions Catalyst Circulation Rate, kg/min 11200 11200 Spent Catalyst Temperature, ° C. 538 538 Regenerator Top Pressure, kPa 177 177 Spent Catalyst Lift Gas 0 0 (not air), m³/min Total Combustion Air, m³/min 1050 1050 Combustion Air to Air 682 682 Grids, m³/min Combustion Air to Spent 368 368 Catalyst Line, m³/min Air from Air Blower to 0 0.35 Upper Zone 148 Air from Air Blower to 0 0 Middle Zone 147 Air from Air Blower to 1 0.65 Lower Zone 146 Catalyst Flow from 0 1 Reactor to Upper Zone 148 Catalyst Flow from 0 0 Reactor to Middle Zone 147 Catalyst Flow from 1 0 Reactor to Lower Zone 146 Catalyst Cooler Duty, kJ/hr 0 0 Carbon on Spent - Regenerated 0.75 0.75 Catalyst, wt % cat H₂ in Coke Burned, wt % 6 6 Delta Nitrogen, wt ppm 112 112 Tuning Catalytic CO Burn Factor 0.5-3 0.5-3 Parameters (CO promoter)

The information in the rows labeled “Geometries” describe the size of the regenerator and the depth (bed level) of the dense phase catalyst bed contained within the regenerator. The top section height refers to the vertical height of the dilute phase catalyst zone within the regeneration vessel. The spent catalyst temperature is the temperature of the coked catalyst particles when introduced to the regeneration vessel. The regenerator top pressure is the pressure of the vapor in the uppermost region of the regenerator. Spent catalyst lift gas refers to the rate of gas (other than air) that is used to transport spent catalyst into the regenerator. Combustion air refers to the total amount of air injected into the regenerator. The relative flow rates of air and catalyst into the different zones of the regenerator are also shown in Table 4. None of these cases include any heat removal from the regenerator via steam generation using a catalyst cooler or other device. The carbon on spent catalyst—regenerated catalyst refers to the change in concentration of carbon on the catalyst as the catalyst passes through the regeneration process. Hydrogen in coke is the percentage of hydrogen in the coke burned in the regenerator. Delta nitrogen refers to the change in concentration of nitrogen on the catalyst as the catalyst passes through the regeneration process.

Table 5 shows results for a base case D and modified case D that are similar to Table 1, except the carrier fluid has been changed to an oxygen-lean carrier fluid, namely a mixture of steam and combustion gas. Specifically, Table 5 shows simulated process results for a base case D in which the distributor 150 is positioned within the lower zone 146 of a dense phase catalyst zone 145 (note that the configuration for base case D is not depicted in FIGS. 1-6). As such, the spent catalyst and carrier fluid mixture is introduced to the first zone 146. Modified case D in contrast places the distributor 150 above the surface 149 of the fluidized catalyst bed 145, thereby introducing the spent catalyst/carrier fluid mixture above the surface 149 of the fluidized catalyst bed 145, as discussed and described above with reference to FIG. 1. For the simulated results shown in Table 5, a high activity level CO promoter was used. The particular CO promoter was platinum at a concentration of 1.5 ppm in the regeneration system. The coke burning rate remains the same, which is 5,350 kg/hr. The cyclone catalyst loading or entrainment rate within the dilute phase catalyst bed 155 was 14.0 kg/min for the base case D and 22.4 tonnes/min for the modified case D.

TABLE 5 Base Modified Case D Case D Carrier fluid introduced via line 129 Combus- Combus- tion Gas tion Gas and Steam and Steam Catalyst Regeneration Temperature, ° C. 712 711 Carbon Content (wt %) on Regenerated Catalyst 0.03 0.01 Carbon Content (wt %) on Spent Catalyst 0.78 0.76 Coke Burning Rate, kg/hr 5350 5350 Total Catalyst Inventory, tonnes 73.8 77.1 First Temperature, ° C. 703 711 Zone 146 of Density, kg/m³ 408 408 Fluidized Superficial Gas Velocity, m/s 0.82 0.83 Catalyst Bed wt % Carbon in Catalyst Bed 0.06 0.01 Conditions CO % mol leaving First Zone 0.43 0.06 NOx ppm leaving First Zone 184 434 O₂ % mol leaving First Zone 8.46 18.05 Coke Burning Rate, kg/hr 3399 861 Catalyst Inventory, tonnes 20 20 Second Temperature, ° C. 712 713 Zone 147 of Density, kg/m³ 402 405 Fluidized Superficial Gas Velocity, m/s 0.88 0.87 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.02 Conditions CO % mol leaving Catalyst Bed 0.25 0.17 NOx ppm leaving Second Zone 204 471 O₂ % mol leaving Second Zone 2.87 8.65 Coke Burning Rate, kg/hr 1768 2674 Catalyst Inventory, tonnes 40.6 40.9 Third Temperature, ° C. 713 659 Zone 148 of Density, kg/m³ 397 150 Fluidized Superficial Gas Velocity, m/s 0.93 0.87 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.26 Conditions CO % mol leaving Third Zone 0.24 0.58 NOx ppm leaving Third Zone 199 107 O₂ % mol leaving Third Zone 2.75 7.81 Coke Burning Rate, kg/hr 45 272 Catalyst Inventory, tonnes 1.43 1.45 Dilute Phase Carbon Content (wt %) 0.02 0.15 Zone 155 CO % mol leaving Dilute Phase 0 0.46 Zone NOx ppm leaving Dilute Phase 263 41 Zone O₂ % mol leaving Dilute Phase 2.14 2.35 Zone Coke Burning Rate, kg/hr 136 1541 Cyclone 165 Cyclone Inlet Temperature, ° C. 715 690 Cyclone Outlet Temperature, ° C. 718 727 Cyclone Catalyst Loading, 14.0 22.4 tonnes/min Flue Gas NOx ppm 263 41 Composition CO % mol 0 0 via line 170 O₂ % mol 2.12 2.12

As shown in Table 5, base case D provides a flue gas via line 170 that contains 265 ppm NOx, while the modified case D provides a flue gas via line 170 that contains only 41 ppm. The CO and carbon present within the regenerator 140 in the upper zone 148 and dilute phase catalyst zone 155 increased for the modified case D over the base case D. The increase in CO and carbon within these zones increases the amount of NOx that can be converted to N₂ within the regenerator 140, thereby providing a flue gas via line 170 having a substantially reduced NOx content for the modified case D versus the base case D. As illustrated in Table 5, the flue gas via line 170 for the modified case D contains about 84.4% less NOx than in base case D (263 ppm NOx for the base case D compared to only 41 ppm NOx for the modified case D).

As shown in Table 5, the temperature of the flue gas at the cyclone 165 inlet for base case D is 715° C., while the temperature of the flue gas at the cyclone 165 outlet is 718° C., which is only a 3° C. temperature difference. However, for the modified case D the temperature of the flue gas at the cyclone 165 inlet is 690° C. and the temperature of the flue gas at the cyclone 165 outlet is 727° C., a 37° C. difference. This increased temperature difference for the modified case D is attributed to afterburning of the CO within the cyclone 165, as discussed and described above with reference to FIG. 1. The increase in temperature within the cyclones 165 and the flue gas via line 170 remains within operationally acceptable ranges, while providing a flue gas having reduced NOx concentrations.

Similar to Table 4, Table 6 shows various operating and other simulation conditions used for the determination of the simulated results.

TABLE 6 Base Modified Case D Case D Geometries Bed Level, m 6.49 6.49 Bed Diameter of Bottom 5.49 5.49 Section, m Top Section Heights, m 8.96 8.96 Top Section Diameter, m 5.49 5.49 Conditions Catalyst Circulation Rate, kg/min 11200 11200 Spent Catalyst Temperature, ° C. 538 538 Regenerator Top Pressure, kPa 177 177 Spent Catalyst Lift Gas 0 315 (not air), m³/min Total Combustion Air, m³/min 1050 1050 Combustion Air from Air 682 1050 Blower, m³/min Combustion Air to Spent 368 0 Catalyst Carrier Line, m³/min Air from Air Blower to 0 0 Upper Zone 148 Air from Air Blower to 0 0 Middle Zone 147 Air from Air Blower to 1 1 Lower Zone 146 Catalyst Flow from 0 1 Reactor to Upper Zone 148 Catalyst Flow from 0 0 Reactor to Middle Zone 147 Catalyst Flow from 1 0 Reactor to Lower Zone 146 Catalyst Cooler Duty, kJ/hr 0 0 Carbon on spent - Regenerated 0.75 0.75 Catalyst, wt % cat H₂ in Coke Burned, wt % 6 6 Delta Nitrogen, wt ppm 112 112 Tuning Catalytic CO Burn Factor 3.0 3.0 Parameters (CO promoter)

Embodiments of the present invention further relate to any one or more of the following paragraphs:

1. A method for regenerating a spent catalyst, comprising: mixing a spent catalyst with a carrier fluid to provide a mixture, wherein the spent catalyst includes carbon deposited on at least a portion thereof, and wherein the carrier fluid comprises an oxygen containing gas; introducing the mixture to or above an upper surface of a dense phase catalyst zone disposed within a regenerator; introducing a gas to a lower zone of the dense phase catalyst zone; and combusting at least a portion of the carbon deposited on the catalyst to provide a flue gas, heat, and a regenerated catalyst.

2. The method according to paragraph 1, wherein the carrier fluid comprises from about 10% to about 90% of the total amount of gas introduced to the regenerator, and wherein the carrier fluid comprises from 0% to about 90% of the total amount of oxygen introduced to the regenerator.

3. The method according to paragraphs 1 or 2, wherein the carrier fluid comprises from about 20% to about 50% of the total amount of gas introduced to the regenerator, and wherein the carrier fluid comprises from about 0% to about 50% of the total amount of oxygen introduced to the regenerator.

4. The method according to paragraph 3, further comprising introducing an oxygen containing gas to the regenerator above the surface of the dense phase catalyst zone.

5. The method according to any of paragraphs 1 to 4, wherein the flue gas comprises less than about 150 ppm nitrogen oxides.

6. The method according to any of paragraphs 1 to 5, wherein introducing the mixture to the upper surface of the dense phase catalyst zone further comprises introducing at least a portion of the mixture to an upper portion of the dense phase catalyst zone disposed below the surface of the dense phase catalyst zone, a dilute phase catalyst zone disposed above the dense phase catalyst zone, or both.

7. The method according to any of paragraphs 1 to 6, wherein the gas comprises an oxygen-lean gas, air, or oxygen-rich gas.

8. The method according to paragraph 7, wherein the ratio of the oxygen introduced with the carrier fluid to the oxygen introduced with the gas ranges from about 1:1 to about 1:3.

9. The method according to any of paragraphs 1 to 8, wherein the carbon deposited on the spent catalyst ranges from about 0.7% wt to about 1.3% wt.

10. The method according to any of paragraphs 1 to 9, further comprising introducing a carbon monoxide combustion promoter to the regenerator.

11. The method according to paragraph 10, wherein the carbon monoxide combustion promoter comprises platinum at a concentration of ranging from about 0.01 ppm to about 3 ppm.

12. A method for regenerating a spent catalyst, comprising: mixing a spent catalyst with a carrier fluid to provide a mixture, wherein the spent catalyst includes carbon deposited on at least a portion thereof; introducing the mixture to a regenerator, wherein the regenerator comprises a dense phase catalyst zone and a dilute phase catalyst zone disposed above the dense phase catalyst zone; and wherein the mixture is introduced to or above an upper surface of the dense phase catalyst zone; introducing a gas to a lower portion of the dense phase catalyst zone; combusting at least a portion of the carbon deposited on the spent catalyst to provide a flue gas, heat, and a regenerated catalyst; introducing at least a portion of the regenerated catalyst to a fluidized catalytic cracker; and recovering the flue gas from the regenerator, wherein the flue gas comprises less than about 150 ppm nitrogen oxides.

13. The method according to paragraph 12, wherein introducing the mixture to or above the upper surface of the dense phase catalyst zone further comprises introducing at least a portion of the mixture to an upper portion of the dense phase catalyst zone disposed below the upper surface of the dense phase catalyst zone, the dilute phase catalyst zone, or both.

14. The method according to paragraphs 12 or 13, wherein the carrier fluid comprises from about 10% to about 90% of a total amount of gas introduced to the regenerator, and wherein the carrier fluid comprises from about 0% to about 90% of the total amount of oxygen introduced to the regenerator.

15. The method of according to any of paragraphs 12 to 14, wherein the carrier fluid comprises less than about 50% of a total amount of gas introduced to the regenerator, and wherein the carrier fluid comprises less than about 50% of the total amount of oxygen introduced to the regenerator.

16. The method of according to any of paragraphs 12 to 15, further comprising introducing air, an oxygen-rich gas, or a combination thereof to the dilute phase catalyst zone.

17. The method according to any of paragraphs 12 to 16, further comprising introducing a carbon monoxide combustion promoter to the regenerator.

18. The method of according to paragraph 17, wherein the concentration of the carbon monoxide combustion promoter ranges from about 0.3 ppm to about 2 ppm

19. A method for regenerating a spent catalyst, comprising: mixing a spent catalyst with a carrier fluid to provide a mixture, wherein the spent catalyst includes carbon deposited on at least a portion thereof; introducing the mixture to a lower zone, an intermediate zone, an upper zone, or any combination thereof of a dense phase catalyst zone disposed below a dilute phase catalyst zone in a regenerator; introducing a gas to the lower zone; introducing an oxygen containing gas to the dilute phase catalyst zone; combusting at least a portion of the carbon deposited on the catalyst to provide a flue gas, heat, and a regenerated catalyst.

20. The method according to paragraph 19, wherein the carrier fluid comprises a gas containing less than about 5% vol oxygen.

21. The method according to paragraphs 19 or 20, wherein the oxygen containing gas comprises a gas mixture containing at least 10% vol oxygen.

22. The method according to any of paragraphs 19 to 21, wherein the gas comprises air, an oxygen-lean gas, or an oxygen-rich gas.

23. The method according to any of paragraphs 19 to 22, wherein the carbon deposited on the spent catalyst ranges from about 0.7% wt to about 1.3% wt.

24. The method according to any of paragraphs 19 to 23, further comprising introducing a carbon monoxide combustion promoter to the regenerator.

25. The method according to paragraph 24, wherein the concentration of the carbon monoxide combustion promoter ranges from about 0.3 ppm to about 2 ppm.

Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values are “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

1. A method for regenerating a spent catalyst, comprising: mixing a spent catalyst with a carrier fluid to provide a mixture, wherein the spent catalyst includes carbon deposited on at least a portion thereof, and wherein the carrier fluid comprises an oxygen containing gas; introducing the mixture to or above an upper surface of a dense phase catalyst zone disposed within a regenerator; introducing a gas to a lower zone of the dense phase catalyst zone; and combusting at least a portion of the carbon deposited on the catalyst to provide a flue gas, heat, and a regenerated catalyst.
 2. The method of claim 1, wherein the carrier fluid comprises from about 10% to about 90% of the total amount of gas introduced to the regenerator, and wherein the carrier fluid comprises from 0% to about 90% of the total amount of oxygen introduced to the regenerator.
 3. The method of claim 1, wherein the carrier fluid comprises from about 20% to about 50% of the total amount of gas introduced to the regenerator, and wherein the carrier fluid comprises from about 0% to about 50% of the total amount of oxygen introduced to the regenerator.
 4. The method of claim 3, further comprising introducing an oxygen containing gas to the regenerator above the surface of the dense phase catalyst zone.
 5. The method of claim 1, wherein the flue gas comprises less than about 150 ppm nitrogen oxides.
 6. The method of claim 1, wherein introducing the mixture to the upper surface of the dense phase catalyst zone further comprises introducing at least a portion of the mixture to an upper portion of the dense phase catalyst zone disposed below the surface of the dense phase catalyst zone, a dilute phase catalyst zone disposed above the dense phase catalyst zone, or both.
 7. The method of claim 1, wherein the gas comprises an oxygen-lean gas, air, or oxygen-rich gas.
 8. The method of claim 7, wherein the ratio of the oxygen introduced with the carrier fluid to the oxygen introduced with the gas ranges from about 1:1 to about 1:3.
 9. The method of claim 1, wherein the carbon deposited on the spent catalyst ranges from about 0.7% wt to about 1.3% wt.
 10. The method of claim 1, further comprising introducing a carbon monoxide combustion promoter to the regenerator.
 11. The method of claim 10, wherein the carbon monoxide combustion promoter comprises platinum at a concentration of ranging from about 0.01 ppm to about 3 ppm.
 12. A method for regenerating a spent catalyst, comprising: mixing a spent catalyst with a carrier fluid to provide a mixture, wherein the spent catalyst includes carbon deposited on at least a portion thereof; introducing the mixture to a regenerator, wherein the regenerator comprises a dense phase catalyst zone and a dilute phase catalyst zone disposed above the dense phase catalyst zone; and wherein the mixture is introduced to or above an upper surface of the dense phase catalyst zone; introducing a gas to a lower portion of the dense phase catalyst zone; combusting at least a portion of the carbon deposited on the spent catalyst to provide a flue gas, heat, and a regenerated catalyst; introducing at least a portion of the regenerated catalyst to a fluidized catalytic cracker; and recovering the flue gas from the regenerator, wherein the flue gas comprises less than about 150 ppm nitrogen oxides.
 13. The method of claim 12, wherein introducing the mixture to or above the upper surface of the dense phase catalyst zone further comprises introducing at least a portion of the mixture to an upper portion of the dense phase catalyst zone disposed below the upper surface of the dense phase catalyst zone, the dilute phase catalyst zone, or both.
 14. The method of claim 12, wherein the carrier fluid comprises from about 10% to about 90% of a total amount of gas introduced to the regenerator, and wherein the carrier fluid comprises from about 0% to about 90% of the total amount of oxygen introduced to the regenerator.
 15. The method of claim 12, wherein the carrier fluid comprises less than about 50% of a total amount of gas introduced to the regenerator, and wherein the carrier fluid comprises less than about 50% of the total amount of oxygen introduced to the regenerator.
 16. The method of claim 12, further comprising introducing air, an oxygen-rich gas, or a combination thereof to the dilute phase catalyst zone.
 17. The method of claim 12, further comprising introducing a carbon monoxide combustion promoter to the regenerator.
 18. The method of claim 17, wherein the concentration of the carbon monoxide combustion promoter ranges from about 0.3 ppm to about 2 ppm.
 19. A method for regenerating a spent catalyst, comprising: mixing a spent catalyst with a carrier fluid to provide a mixture, wherein the spent catalyst includes carbon deposited on at least a portion thereof; introducing the mixture to a lower zone, an intermediate zone, an upper zone, or any combination thereof of a dense phase catalyst zone disposed below a dilute phase catalyst zone in a regenerator; introducing a gas to the lower zone; introducing an oxygen containing gas to the dilute phase catalyst zone; combusting at least a portion of the carbon deposited on the catalyst to provide a flue gas, heat, and a regenerated catalyst.
 20. The method of claim 19, wherein the carrier fluid comprises a gas containing less than about 5% vol oxygen.
 21. The method of claim 19, wherein the oxygen containing gas comprises a gas mixture containing at least 10% vol oxygen.
 22. The method of claim 19, wherein the gas comprises air, an oxygen-lean gas, or an oxygen-rich gas.
 23. The method of claim 19, wherein the carbon deposited on the spent catalyst ranges from about 0.7% wt to about 1.3% wt.
 24. The method of claim 19, further comprising introducing a carbon monoxide combustion promoter to the regenerator.
 25. The method of claim 24, wherein the concentration of the carbon monoxide combustion promoter ranges from about 0.3 ppm to about 2 ppm. 